Method of resin transfer molding a composite article

Abstract

In a resin transfer molding process a preform is positioned in the cavity of a molding tool, the molding tool is closed and resin is introduced into the cavity. The preform is a resin transfer molding core with fiber reinforcement material affixed to its outer surface. Internal communication passages extend within the interior of the core, a first and a second internal communication passage each having an inlet opening and a discharge opening extending through the outer surface of the core. The molding tool has a first port and a second port. Fluid-tight communication is formed between the first port and the inlet opening of the first internal communication passage. Fluid-tight communication also is formed between the second port and the discharge opening of the second internal communication passage. Uncured resin is introduced into the cavity through the first port, to and through the inlet opening of the first internal communication passage. The cavity is vented through the discharge opening of the second internal communication passage, to and through the second port. The resin is cured to provide a fiber reinforced composite structure.

I claim: 
     
       1. A method of resin transfer molding a composite structure, which method comprises: (A) providing a core having an outer surface and comprising a plurality of internal communication passages within the core, at least a first of said internal communication passages having an inlet opening and at least one discharge opening extending through the outer surface of said core, and at least a second of said internal communication passages having a discharge opening extending through said outer surface of the core and at least one inlet opening wherein said first internal communication passage does not intersect said second internal communication passage within the core;   (B) affixing fiber reinforcement material to said outer surface of said core to form a resin transfer molding preform;   (C) positioning said preform in a cavity of a molding tool having a first port and a second port;   (D) closing said molding tool and forming a fluid-tight communication between said first port and said inlet opening of said first internal communication passage and forming a fluid-tight communication between said second port and said discharge opening of said second internal communication passage;   (E) introducing uncured resin into said cavity through said first port, to and through said inlet opening of said first internal communication passage, and venting said cavity through said discharge opening of said second internal communication passage, to and through said second port; and   (F) curing said resin to provide said composite structure.   
     
     
       2. The method of claim 1, wherein said core comprises a substantially solid body of foam. 
     
     
       3. The method of claim 2, wherein said foam is structural polyurethane foam. 
     
     
       4. The method of claim 2, wherein said foam itself forms said internal communication passages. 
     
     
       5. The method of claim 2, wherein said internal communication passages are formed by tubes embedded within said foam. 
     
     
       6. The method of claim 5, wherein said tubes comprise flexible plastic. 
     
     
       7. The method of claim 1, further comprising the step of removing at least a portion of said core from said composite structure. 
     
     
       8. The method of claim 1, wherein subsequent to commencing step (E) and prior to step (F), venting said cavity through said discharge opening of said second internal communication passage is terminated and pressure greater than atmospheric pressure is applied to said discharge opening of said second internal communication passage. 
     
     
       9. The method of claim 8, wherein said pressure is applied by introducing additional said resin into said discharge opening of said second internal communication passage. 
     
     
       10. A method of resin transfer molding a composite structure, which method comprises: (A) providing a core having an outer surface and comprising a plurality of internal communication passages within the core, at least a first of said internal communication passages having an inlet opening and at least one discharge opening extending through the outer surface of said core, and at least a second of said internal communication passages having a discharge opening extending through said outer surface of the core and at least one inlet opening;   (B) affixing fiber reinforcement material to said outer surface of said core to form a resin transfer molding preform;   (C) positioning said preform in a cavity of a molding tool having a first port and a second port;   (D) closing said molding tool and forming a fluid-tight communication between said first port and said inlet opening of said first internal communication passage and forming a fluid-tight communication between said second port and said discharge opening of said second internal communication passage;   (E) introducing uncured resin into said cavity through said first port, to and through said inlet opening of said first internal communication passage, and venting said cavity through said discharge opening of said second internal communication passage, to and through said second port, said venting then being terminated and pressure greater than atmospheric pressure being applied to said discharge opening of said second internal communication passage, after sensing the presence of resin within said second internal communication passage, by introducing additional said resin into said discharge opening of said second internal communication passage; and   (F) curing said resin to provide said composite structure.   
     
     
       11. The method of claim 10, wherein said sensing comprises sensing the temperature at a location within said second internal communication passage. 
     
     
       12. The method of claim 10, wherein said sensing comprises optically sensing the presence of resin at a location within said second internal communication passage. 
     
     
       13. The method of claim 1, further comprising the step of introducing gaseous fluid into at least one of said internal communication passages to evacuate resin therefrom subsequent to step (E) and prior to step (F). 
     
     
       14. The method of claim 1, wherein said venting comprises drawing a vacuum in said second internal communication passage.